On Monday, a report by three Japanese utilities said that the Tomari nuclear plant in Hokkaido and the Tsuruga plant in Fukui Prefecture are at risk of earthquakes that exceed their designed quake-resistance parameters.
A day later on Tuesday, Japan’s Nuclear and Industrial Safety Agency (NISA) suggested the possibility of an old fault “fracture zone” right beneath the Number 1 and Number 2 units of the Tsuruga nuclear plant moving closely with an active fault nearby, and subsequently issued the inspection order on Tuesday to the Japan Atomic Power Company, after a team of experts surveyed 3 faults in the compound and found that one of them located 150 meters west of the No.2 reactor may be active.
According to NISA, a 35-km-long fault named Urazoko runs beneath the compound of the Tsuruga power plant, and experts believe it caused an earthquake there around 4,500 years ago or later. The team said the fault could shift simultaneously with a known active fault nearby. If that happens, they could trigger an earthquake more powerful than the plant is supposed to withstand.
Japan has rules against installing a nuclear plant on top of an active fault that has moved within the last 120,000 to 130,000 years, and some are concerned that the Tsuruga site may be declared unfit to host a nuclear plant.
Katsuhiko Ishibashi, honorary professor at Kobe University, said of the Tsuruga nuclear power plant, “It was not a proper place to build (a nuclear facility) in the first place. What is more, if a fault beneath the reactor buildings can move in tandem with an active fault, the location is clearly disqualified (as a site for a nuclear facility).
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